Peer Reviewed

Peer-Reviewed

Abstract

High nitrogen (N) fertiliser costs and sustainability concerns have increased interest in cultivating legume crops in the inter-row in coppiced plantation crops. Supplemental N fertiliser applications are likely needed in such systems because the availability of legume-derived N may not match peak tree N demand, but this added N fertiliser will likely suppress biological N2 fixation (%BNF) in the inter-row legumes. We hypothesised that some legume species may be less susceptible to N fertiliser-induced suppression of %BNF and are therefore better suited as legume inter-row crops. We compared the impact of four rates of N fertiliser (0, 50, 100 and 150 kg N ha−1) on %BNF in faba bean (Vicia faba) and chickpea (Cicer arietinum) when cultivated as inter-row legume crops in an established Melaleuca alternifolia plantation and as a monoculture in a glasshouse pots trial. N2fixation was not completely suppressed in either species at 150 kg N ha−1, with around 40 %BNF maintained in faba bean in the field and glasshouse and around 35 %BNF and 23 %BNF maintained in chickpea in the field and glasshouse, respectively. Faba bean had significantly higher %BNF than chickpea at 100 kg N ha−1 when intercropped in the field, and at 100 and 150 kg N ha−1 in the glasshouse, associated with a higher shoot N demand in faba bean. The results suggest that where soil conditions are suitable for either species, faba bean is more suitable as a green manure intercrop than chickpea when supplementary N fertiliser additions are required.